The present invention relates to a brazing apparatus using an electromagnetic induction pump. More specifically, the present invention relates to a brazing apparatus having a pluralty of reservoirs for brazing filler metal, wherein the height of the reservoirs may be adjusted independently. The present invention also relates to a brazing apparatus having an intermediate processing space capable of accommodating an intermediate processing device such as a warp correcting device or a flux applying device. The present invention also relates to a brazing apparatus having a pluralty of reservoirs fitted with local nozzles capable of soldering a local area of a workpiece. In this latter arrangement, there is no restriction as to the orientation of the reservoirs with respect to each other and multiple workpieces may be processed simultaneously.
FIG. 15 shows the general structure of a conventional wave soldering device, wherein a work conveyor 14 adapted to convey workpieces to be soldered, such as component-mounted substrates or the like, extends from a workpiece inlet 12 to a workpiece outlet 13 of a device cover 11.
A fluxer 15 for applying foamed flux to workpieces, a preheater 16 for preheating the workpieces, a solder bath 17 for soldering the workpieces by using molten solder ejected from wave nozzles, and a fan 18 for cooling the workpieces after soldering are arranged in this order along the conveyor 14.
A primary wave nozzle 21a and a secondary wave nozzle 21b are disposed in the solder bath 17. A wave-forming plate 22 has numerous ejection holes is disposed at the open top of the primary wave nozzle 21a. The primary wave nozzle 21a is adapted to feed molten solder over the entire workpiece, covering every corner of the electrode portions and other parts of chip components by means of numerous small primary waves W1 which are ejected as irregular spouts from the ejection holes of the wave-forming plate 22. The secondary wave nozzle 21b is adapted to adjust the shapes of soldered parts by means of gentle secondary waves W2.
As shown in FIG. 16, the solder bath 17 is provided with a pressure duct 23 fitted in an opening at the bottom of the nozzle body 21 of the wave nozzles 21a,21b, and a pump impeller 24 disposed at the end of the pressure duct 23. The solder bath 17 also includes a suction opening 25 and a motor drive mechanism 26 associated with the pump impeller 24.
Molten solder introduced from the suction opening 25 as a result of rotation of the pump impeller 24 is fed under pressure through the pressure duct 23 into the nozzle body 21 and emitted from the nozzle body 21 in waves so that the undersides of workpieces P, which may be component-mounted substrates, are soldered while they are conveyed, being held between conveyor claws 27 of the conveyor 14. The major part of the solder waves directly returns onto the molten solder surface 28 in the solder bath 17 and is circulated into the suction opening 25 of the pump impeller 24.
Various brazing apparatuses using an electromagnetic pump are disclosed in, for example, Japanese Patent Publication Nos. 42590-1976, 31628-1990 and 60581-1991, and Japanese Utility Model Publication No. 17572-1988. Electromagnetic pumps used in those brazing apparatuses are either a direct current type or an alternating current type.
A direct-current type electromagnetic pump is adapted to generate a thrusting force to a conductive brazing filler metal, such as tin, over its path of motion by applying a magnetic field perpendicularly to the path of the conductive brazing filler metal and feeding direct electric current perpendicularly to both the path of motion and the magnetic field.
An alternating-current type electromagnetic pump is an electromagnetic induction pump which includes induction coils arranged on a plane along a path traveled by a conductive brazing filler metal and is adapted to generate a thrusting force to the brazing filler metal by feeding AC current having lagged phases to the induction coils, thereby generating a shifting magnetic field in the path traveled by the conductive brazing filler metal to permit the electromagnetic induction to generate electromotive force on the conductive brazing filler metal in its path of motion so that electric current generated by the electromotive force of the brazing filler metal flows in the magnetic flux in the magnetic field.
With a wave soldering device of a type which calls for force-feeding molten solder by means of a pump impeller rotated by a conventional motor drive mechanism, it is difficult to reduce the amount of solder, because of structural limitations in how small the solder bath can be.
To be more precise, as the solder bath has 17 to be sufficiently deep in order to prevent oxidized solder from being entangled in the portion where the impeller is turning, the volume of the entire solder bath 17 becomes large.
On the other hand, although a conventional brazing apparatus which calls for force-feeding brazing filler metal by using an electromagnetic pump and ejecting it in the form of waves requires less brazing filler metal compared with the wave soldering device described above, it occupies a considerable space along the conveyance path of workpieces.
For this reason, unlike a motor-driven wave soldering device, no conventional electromagnetic pump type brazing apparatus has ever employed the art that calls for serially arranging two brazing apparatus and performing two kinds of brazing by means of primary waves and secondary waves.
Simply arranging two conventional electromagnetic pump type brazing apparatuses to be used respectively for primary brazing and secondary brazing would not only double the surface area of the device, which would tale up too much space, but also require twice as much brazing filler metal.
Due to environmental protection regulations, the demands for brazing filler metal which does not contain lead (what is generally called lead-free solder) are recently on the increase. As lead-free solders are made of materials such as indium or the like, which are 3 to 10 times as expensive as ordinary solder made of tin and lead, it is necessary to reduce the quantity of the brazing filler metal to be used as much as possible.
In order to solve the above problems, an object of the present invention is to provide an electromagnetic pump type brazing apparatus which is capable of forming waves at a plurality of locations without taldng up much space. Another object of the present invention is to provide an electromagnetic pump type brazing apparatus which is capable of reducing the quantity of brazing filler metal.
Briefly stated, the present invention is a brazing apparatus having at least a first and second reservoir for holding a brazing filler metal. The first and second reservoirs are disposed along a predetermined conveyance path of a workpiece. A first nozzle is disposed on and in communication with the first reservoir and ejects a first wave of brazing filler metal from the first reservoir. A second nozzle is disposed on and in communication with the second reservoir and ejects a second wave of brazing filler metal from the second reservoir. A means for adjusting the height of the first and second reservoirs allows for the height of the reservoirs to be adjusted independently from one another.
In an embodiment of the present invention, a brazing apparatus is provided including a plurality of reservoirs adapted to contain brazing filler metal, and a plurality of electromagnetic induction pumps adapted to braze workpieces by ejecting upward the brazing filler metal contained in the reservoirs, said reservoirs arranged along the predetermined conveyance path of workpiece and having vertically extending vertical plate portions in the shape of a plate, and the electromagnetic induction pumps disposed respectively along specified vertical plate portions of the reservoirs.
With the configuration as above, providing a plurality of reservoirs enables the brazing based on different criteria for the respective reservoirs, and the plurality of electromagnetic induction pumps installed along vertical plate portions of the respective reservoirs take up only a limited space so that a compact brazing apparatus which is capable of forming more than one type of waves is provided.
According to another feature of the invention, a reservoir of the brazing apparatus includes a pump reservoir portion which is vertically installed and provided with an electromagnetic induction pump, and a wave forming portion which is formed above the pump reservoir portion and adapted to form waves.
As each pump reservoir portion including an electromagnetic induction pump is so disposed as to extend vertically, with a wave forming portion formed above the pump reservoir portion, the quantity of brazing filler metal to be contained in the reservoir can be reduced.
According to another feature of the invetion, each electromagnetic induction pump of brazing apparatus comprises a first iron core disposed in contact with the outer side face of a vertical plate portion, an induction coil wound around the first iron core, a second iron core dissposed in parallel to the inner side face of the vertical plate portion and the second iron core.
As the first iron cores around which the induction coils are wound are disposed outside the vertical plate portions of the respective reservoirs, maintenance of the induction coils or a similar operation can be easily done from the outside.
According to yet another feature of the invention, the brazing apparatus includes separate sets of heaters which are disposed in the plurality of reservoirs.
With the configuration as above, the temperatures of the brazing filler metal in the reservoirs can be respectively and independently controlled whenever such a separate control is necessary.
In addition, according to another feature of the invention, the brazing apparatus includes a plurality of removable nozzles which are respectively disposed on the electromagnetic induction pumps and are adapted to eject brazing filler metal therefrom.
With the configuration as above, maintenance of the nozzles themselves or cleaning of the inside of an electromagnetic induction pump can be easily done by removing the nozzle.
According to yet another feature of the invention, the brazing apparatus includes height adjusting means for adjusting the height of a reservoir or the heights of reservoirs.
With the configurations as above, in cases where the inclination of the workpiece conveyance path has been changed or where a height adjustment has otherwise become necessary, the optimal distances between workpiece and waves can be obtained by adjusting the relative heights of the reservoirs with respect to one another or adjusting the absolute heights of the reservoir from a given installation surface.
According to an embodiment of the invention, a brazing apparatus is provided comprising a first reservoir for holding a brazing filler metal. The first reservoir is disposed underneath a workpiece. There is also a second reservoir for holding a brazing filler metal. The second reservoir is disposed adjacent to the first reservoir. A first local nozzle is disposed on and in communication with the first reservoir, for ejecting upwardly a first wave of brazing filler metal from the first reservoir. A second local nozzle is disposed on and in communication with the second reservoir, for ejecting upwardly a second wave of said brazing filler metal from said second reservoir. An interference preventing space is located between the first and second local nozzles and is effective to prevent interference between a workpiece and the local nozzles and between multiple workpieces being brazed simultaneously. A means for adjusting the height of said first and second reservoirs to allow said height of each of said first and second reservoirs to be adjusted independently is provided. Finally, a means for adjusting the position of the workpiece relative to the first and second reservoirs is provided.